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        <p>摘要：JavaScript数组API很多，如果不经常用的话很容易忘记，所以先总结一下js的数组方法.</p>
<hr>
<blockquote>
<p>数组特点：</p>
</blockquote>
<pre><code>数组定义时无需指定数据类型
数组定义时可以无需指定数组长度
数组可以存储任何数据类型的数据
</code></pre><blockquote>
<p>JavaScript中创建数组有两种方式</p>
</blockquote>
<p>(一) 使用Array构造函数<br>var arr=new Array(值1,值2,值3); //直接实例化<br>var array=new Array(size);  //创建数组并指定长度</p>
<p>(二) 使用数组字面量表示法：<br>var arr=[值1,值2,值3];    //隐式创建</p>
<p>数组的方法有数组原型方法，也有从object对象继承来的方法，这里我们只介绍数组的原型方法，数组原型方法主要有以下这些：</p>
<p>join()<br>push()和pop()<br>shift() 和 unshift()<br>sort()<br>reverse()<br>concat()<br>slice()<br>splice()<br>indexOf()和 lastIndexOf() （ES5新增）<br>forEach() （ES5新增）<br>map() （ES5新增）<br>filter() （ES5新增）<br>every() （ES5新增）<br>some() （ES5新增）<br>reduce()和 reduceRight() （ES5新增）</p>
<h2 id="数组API"><a href="#数组API" class="headerlink" title="数组API"></a>数组API</h2><h3 id="数组转化为字符串"><a href="#数组转化为字符串" class="headerlink" title="数组转化为字符串"></a>数组转化为字符串</h3><p>1、 将数组转化为字符串并分隔每个元素<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arr = [<span class="number">1</span>,<span class="number">2</span>,<span class="number">33</span>]</span><br><span class="line"><span class="built_in">console</span>.log(<span class="built_in">String</span>(arr))</span><br></pre></td></tr></table></figure></p>
<p>2、 将数组转化为字符串，可定义分隔符<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arr = [<span class="number">1</span>,<span class="number">2</span>,<span class="number">3</span>];</span><br><span class="line"><span class="built_in">console</span>.log(arr.join()); <span class="comment">// 1,2,3</span></span><br><span class="line"><span class="built_in">console</span>.log(arr.join(<span class="string">"-"</span>)); <span class="comment">// 1-2-3</span></span><br><span class="line"><span class="built_in">console</span>.log(arr); <span class="comment">// [1, 2, 3]（原数组不变）</span></span><br></pre></td></tr></table></figure></p>
<p>通过join()方法可以实现重复字符串，只需传入字符串以及重复的次数，就能返回重复后的字符串，函数如下：<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">repeatString</span>(<span class="params">str, n</span>) </span>&#123;</span><br><span class="line"><span class="keyword">return</span> <span class="keyword">new</span> <span class="built_in">Array</span>(n + <span class="number">1</span>).join(str);</span><br><span class="line">&#125;</span><br><span class="line"><span class="built_in">console</span>.log(repeatString(<span class="string">"abc"</span>, <span class="number">3</span>)); <span class="comment">// abcabcabc</span></span><br></pre></td></tr></table></figure></p>
<h3 id="结尾出入栈"><a href="#结尾出入栈" class="headerlink" title="结尾出入栈"></a>结尾出入栈</h3><p>1、入栈：arr.push(值)<br>    将值压入数组结尾，并返回修改后数组的长度<br>2、出栈：var last=arr.pop();<br>    弹出数组最后一个元素，减少数组的 length 值，然后返回移除的项<br>优点：每次出入栈，不影响其余元素的位置</p>
<h3 id="开头出入栈"><a href="#开头出入栈" class="headerlink" title="开头出入栈"></a>开头出入栈</h3><p>1、入栈：arr.unshift(值);<br>    将值插入数组开头，并返回数组的长度<br>2、出栈：var first=arr.shift();<br>    取出数组第一个元素，并返回删除元素的值；如果数组为空则返回undefined<br>缺点：每次出入栈，其余元素的位置都要顺移1</p>
<h3 id="升序排列"><a href="#升序排列" class="headerlink" title="升序排列"></a>升序排列</h3><p>sort()：按升序排列数组项——即最小的值位于最前面，最大的值排在最后面，直接修改原数组<br>特点：将arr中的元素，以字符串方式升序<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arr1 = [<span class="string">"a"</span>, <span class="string">"d"</span>, <span class="string">"c"</span>, <span class="string">"b"</span>];</span><br><span class="line"><span class="built_in">console</span>.log(arr1.sort()); <span class="comment">// ["a", "b", "c", "d"]</span></span><br><span class="line">arr2 = [<span class="number">13</span>, <span class="number">24</span>, <span class="number">51</span>, <span class="number">3</span>];</span><br><span class="line"><span class="built_in">console</span>.log(arr2.sort()); <span class="comment">// [13, 24, 3, 51]</span></span><br><span class="line"><span class="built_in">console</span>.log(arr2); <span class="comment">// [13, 24, 3, 51](原数组被改变)</span></span><br></pre></td></tr></table></figure></p>
<p>为了解决上述问题，sort()方法可以接收一个比较函数作为参数，以便我们指定哪个值位于哪个值的前面。<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arr = [<span class="number">13</span>, <span class="number">24</span>, <span class="number">3</span>, <span class="number">51</span>] </span><br><span class="line">arr.sort(<span class="function"><span class="keyword">function</span>(<span class="params">a,b</span>)</span>&#123;</span><br><span class="line">    <span class="keyword">return</span> a-b  <span class="comment">//升序</span></span><br><span class="line">&#125;)</span><br><span class="line">arr.sort(<span class="function"><span class="keyword">function</span>(<span class="params">a,b</span>)</span>&#123;</span><br><span class="line">    <span class="keyword">return</span> b-a  <span class="comment">//降序</span></span><br><span class="line">&#125;)</span><br></pre></td></tr></table></figure></p>
<h3 id="反转数组元素-原数组改变"><a href="#反转数组元素-原数组改变" class="headerlink" title="反转数组元素(原数组改变)"></a>反转数组元素(原数组改变)</h3><p>reverse()：反转数组项的顺序<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arr = [<span class="number">13</span>, <span class="number">24</span>, <span class="number">51</span>, <span class="number">3</span>];</span><br><span class="line"><span class="built_in">console</span>.log(arr.reverse()); <span class="comment">//[3, 51, 24, 13]</span></span><br><span class="line"><span class="built_in">console</span>.log(arr); <span class="comment">//[3, 51, 24, 13](原数组改变)</span></span><br></pre></td></tr></table></figure></p>
<h3 id="连接和获取数组-原数组不改变"><a href="#连接和获取数组-原数组不改变" class="headerlink" title="连接和获取数组(原数组不改变)"></a>连接和获取数组(原数组不改变)</h3><p>1、 连接:concat()将参数添加到原数组中，原数组不改变<br>var newArr=arr1.concat(值1,值2,arr2,…);<br>将concat后的内容，和arr1拼接，组成新数组返回<br>强调：concat的参数中包含数组，则打散数组，以单个元素拼接<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arr = [<span class="number">1</span>,<span class="number">3</span>,<span class="number">5</span>,<span class="number">7</span>];</span><br><span class="line"><span class="keyword">var</span> arrCopy = arr.concat(<span class="number">9</span>,[<span class="number">11</span>,<span class="number">13</span>]);</span><br><span class="line"><span class="built_in">console</span>.log(arrCopy); <span class="comment">//[1, 3, 5, 7, 9, 11, 13]</span></span><br><span class="line"><span class="built_in">console</span>.log(arr); <span class="comment">// [1, 3, 5, 7](原数组未被修改)</span></span><br></pre></td></tr></table></figure></p>
<p><code>注意</code>：如果连接的是二维数组的话<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arrCopy2 = arr.concat([<span class="number">9</span>,[<span class="number">11</span>,<span class="number">13</span>]]);</span><br><span class="line"><span class="built_in">console</span>.log(arrCopy2); <span class="comment">//[1, 3, 5, 7, 9, Array[2]]</span></span><br><span class="line"><span class="built_in">console</span>.log(arrCopy2[<span class="number">5</span>]); <span class="comment">//[11, 13]</span></span><br></pre></td></tr></table></figure></p>
<p>concat方法只能将传入数组中的每一项添加到数组中，如果传入数组中有些项是数组，那么也会把这一数组项当作一项添加到arrCopy2中</p>
<p>2、 获取数组<br>slice()：返回从原数组中指定开始下标到结束下标之间的项组成的新数组，原数组不改变<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arr = [<span class="number">1</span>,<span class="number">2</span>,<span class="number">3</span>,<span class="number">4</span>]</span><br><span class="line">subArr=arr.slice(starti,endi+<span class="number">1</span>);</span><br></pre></td></tr></table></figure></p>
<p>获得arr中starti位置开始，到endi位置的所有元素组成的新数组<br>强调：含头不含尾<br>省略第二个参数：表示从starti一直取到结尾<br>可支持负数参数：-n表示倒数第n个元素，相当于length-n</p>
<h3 id="删除，插入，替换：（直接修改原数组）"><a href="#删除，插入，替换：（直接修改原数组）" class="headerlink" title="删除，插入，替换：（直接修改原数组）"></a>删除，插入，替换：（直接修改原数组）</h3><p>splice()：很强大的数组方法，它有很多种用法，可以实现删除、插入和替换<br>1、删除：可以删除任意数量的项，只需指定 2 个参数：要删除的第一项的位置和要删除的项数。<br>2、插入：可以向指定位置插入任意数量的项，只需提供 3 个参数：起始位置、 0（要删除的项数）和要插入的项。<br>3、替换：可以向指定位置插入任意数量的项，且同时删除任意数量的项，只需指定 3 个参数：起始位置、要删除的项数和要插入的任意数量的项。插入的项数不必与删除的项数相等。<br><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> arr = [<span class="number">1</span>,<span class="number">3</span>,<span class="number">5</span>,<span class="number">7</span>,<span class="number">9</span>,<span class="number">11</span>];</span><br><span class="line"><span class="keyword">var</span> arrRemoved = arr.splice(<span class="number">0</span>,<span class="number">2</span>);</span><br><span class="line"><span class="built_in">console</span>.log(arr); <span class="comment">//[5, 7, 9, 11]</span></span><br><span class="line"><span class="built_in">console</span>.log(arrRemoved); <span class="comment">//[1, 3]</span></span><br><span class="line"><span class="keyword">var</span> arrRemoved2 = arr.splice(<span class="number">2</span>,<span class="number">0</span>,<span class="number">4</span>,<span class="number">6</span>);</span><br><span class="line"><span class="built_in">console</span>.log(arr); <span class="comment">// [5, 7, 4, 6, 9, 11]</span></span><br><span class="line"><span class="built_in">console</span>.log(arrRemoved2); <span class="comment">// []</span></span><br><span class="line"><span class="keyword">var</span> arrRemoved3 = arr.splice(<span class="number">1</span>,<span class="number">1</span>,<span class="number">2</span>,<span class="number">4</span>);</span><br><span class="line"><span class="built_in">console</span>.log(arr); <span class="comment">// [5, 2, 4, 4, 6, 9, 11]</span></span><br><span class="line"><span class="built_in">console</span>.log(arrRemoved3); <span class="comment">//[7]</span></span><br></pre></td></tr></table></figure></p>
<h3 id="indexOf-和lastindexOf"><a href="#indexOf-和lastindexOf" class="headerlink" title="indexOf()和lastindexOf()"></a>indexOf()和lastindexOf()</h3><p>indexOf()：接收两个参数：要查找的项和（可选的）表示查找起点位置的索引。其中，从数组的开头（位置 0）开始向后查找。<br>lastindexOf()：顾名思义，这个是从数组的末尾开始向后查找</p>
<blockquote>
<p>这两个方法都返回要查找的项在数组中的位置，或者在没找到的情况下返回-1。在比较第一个参数与数组中的每一项时，会使用全等操作符。</p>
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